<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<script type="text/javascript">
			window.onload = function() {
				var button = document.getElementsByTagName("input")[2];
				button.onclick = function() {
					console.log("onclick");
				}
			
			}
		</script>
	</head>
	<body>
		<input type="button" onclick="alert('dfdf')" value="click"><br />
		<input type="button" onclick="cli()" onmouseover="over()"><br />
		<input type="button" value="click">
	</body>
</html>
